The use of polymeric materials in medical devices for implantation or insertion into the body of a patient is common in the practice of modern medicine. For example, polymeric materials such as silicone rubber, polyurethane, and fluoropolymers, for instance, polytetrafluoroethylene (PTFE), expanded PTFE (ePTFE) and ethylene tetrafluoroethylene (ETFE), are used as coating materials/insulation for medical leads, providing mechanical protection, electrical insulation, or both.
As another example, drug eluting stents are known which have polymeric coatings over the stent that release a drug to counteract the effects of in-stent restenosis. Specific examples of drug eluting coronary stents include commercially available stents from Boston Scientific Corp. (TAXUS, PROMUS), Johnson & Johnson (CYPHER), and others. See S. V. Ranade et al., Acta Biomater. 2005 January; 1(1): 137-44 and R. Virmani et al., Circulation 2004 Feb. 17, 109(6): 701-5. Various types of polymeric materials have been used in such polymeric coatings including, for example, homopolymers such as poly(n-butyl methacrylate) and copolymers such as poly(ethylene-co-vinyl acetate), poly(vinylidene fluoride-co-hexafluoropropylene), and poly(styrene-b-isobutylene-b-styrene) triblock copolymers (SIBS). SIBS triblock copolymers have a soft, elastomeric low glass transition temperature (Tg) midblock and hard elevated Tg endblocks. Consequently, SIBS copolymers are thermoplastic elastomers, in other words, elastomeric (i.e., reversibly deformable) polymers that form physical crosslinks which can be reversed by melting the polymer (or, in the case of SIBS, by dissolving the polymer in a suitable solvent). SIBS is also highly biocompatible and biostable.